Cyclospora cayetanensis or Clostridium difficile: Who Caused the Diarrhea?

Cyclospora cayetanensis, a parasite causing human enteritis, has been rarely reported from healthcare laboratories despite its universal presence. While it is usually responsible for self-limiting diarrhea in immunocompetent individuals, we present a case where the patient suffered from severe, unrelenting diarrhea despite having no obvious immune defects. Additionally, there was no history of international travel or consumption of outside food or water. A week after testing positive only for Cyclospora, the patient tested positive for Clostridium difficile as well, and her diarrhea showed no signs of improvement. This posed a dilemma for the clinicians, as the patient was suffering from diarrhea even when she had tested negative for C. difficile, but she recovered only when fidaxomicin was prescribed. To add to the perplexion, Cyclospora remained positive in her stool even after the completion of the prescribed treatment. Several hypotheses have been derived from this unusual case, and the most probable one seems to be a case of coinfection; however, such a coinfection has never been reported in the literature. This case report serves as a unique opportunity to explore the possible mechanisms that may have led to this condition.